New viaduct on Route 16 should open Monday

There’s good and bad news for those who drive eastbound state Route 16 through Tacoma’s Nalley Valley.

The good news is that if the weather cooperates you’ll be driving on the permanent viaduct come Monday morning. The bad news is major traffic delays this weekend as crews pave the connection between the old and new viaducts.

State Department of Transportation officials will decide Thursday whether weekend weather will be dry enough for the paving. If so, work is scheduled to start at 10 p.m. Friday and extend through early Monday.

Backups will be the heaviest Saturday and Sunday, said Claudia Bingham-Baker, spokeswoman for the Transportation Department. With an average of 100,000 vehicles traveling the eastbound lanes on a typical weekend, backups could extend 6 miles to the Tacoma Narrows Bridge.

Crews will close all eastbound lanes of state Route 16 at South Union Avenue in Tacoma and detour drivers off Union Avenue. Also closed overnight Friday will be the South Union Avenue on-ramp to eastbound state Route 16 and the southbound Interstate 5 exit to South 38th Street.

To accommodate the increase in daytime traffic, crews will open two eastbound lanes at 7:30 a.m. Saturday, directing drivers to northbound and southbound I-5, as well as the on-ramp and I-5 exit.

Nighttime closures will be the same Saturday and Sunday.

At 11:30 a.m. Sunday, one lane of eastbound state Route 16 will open and all eastbound traffic will be diverted to southbound I-5. Those wanting to reach northbound I-5 will have to get off at the South 56th Street interchange.

“When people drive through on Monday morning, they’ll be driving on the new viaduct,” Bingham-Baker said.

The old viaduct eventually will be torn down as part of the Nalley Valley overhaul, a $500 million project meant to streamline the busiest intersection in Pierce County at I-5 and state Route 16.

The first phase of the project took 2.5 years and cost $184 million. It included building 10 bridges, pouring 48,000 cubic yards of concrete and sinking 77 supporting piers as deep as 70 feet. That phase was finished in June 2011.

The eastbound portion of the project will run a $115 million tab, according to the Transportation Department. It will relocate the eastbound mainline, build seven bridges and construct the Sprague ramps.